Windows Server 2008 R2 : Deploying and Using Windows Virtualization - Quick Migration and Live Migration (part 1)

Although both technologies achieve the same thing—moving virtual servers between Hyper-V hosts—they use different methods and mechanisms to achieve it. Both require at least two Hyper-V host servers in a cluster, attached to the same shared storage system. Usually, the shared storage is an iSCSI or Fibre Channel storage area network (SAN).

Quick Migration

Quick Migration provides a way to quickly move a virtual machine from one host server to another with a small amount of downtime.

In a Quick Migration, the guest virtual machine is suspended on one host and resumed on another host. This operation happens in the time it takes to transfer the active memory of the virtual machine over the network from the first host to the second host. For a host with 8GB of RAM, this might take about two minutes using a 1GB iSCSI connection.

Quick Migration was the fastest migration available for Windows Server 2008 Hyper-V. Microsoft made considerable investments in Hyper-V migration technologies, trying to reduce the time required to migrate virtual machines between Hyper-V hosts. The result was Live Migration, which has the same hardware requirements as Quick Migration, but with a near instantaneous failover time.

Live Migration

Since the release of Hyper-V V1 with Windows Server 2008, the number-one most-requested feature by customers is the ability to migrate running virtual machines between hosts, with no downtime. VMware’s VMotion has been able to do this for some time. Finally, with Windows Server 2008 R2, it can be done natively with Hyper-V for no extra cost. This makes it a compelling reason to move to Hyper-V.

Live Migration uses failover clustering. The quorum model used for your cluster will depend on the number of Hyper-V nodes in your cluster. In this example, we will use two Hyper-V nodes in a Node and Disk Majority Cluster configuration. There will be one shared storage LUN used as the cluster quorum disk and another used as the Cluster Shared Volume (CSV) disk.

This section describes how to use Hyper-V Live Migration to move virtual machines between clustered Hyper-V hosts.

Configuring the Cluster Quorum Witness Disk

Live Migration requires a Windows Server 2008 R2 cluster configured to use shared storage. Typically, these are LUNs provisioned on an iSCSI or Fibre Channel SAN. One LUN will be used as the witness disk for quorum and another will be used as a Cluster Shared Volume (CSV) to store the virtual machine images.

The LUN for the shared witness quorum disk must be configured before the cluster is formed, so that cluster manager can configure the cluster properly. Connect this LUN via iSCSI or Fibre Channel to both nodes you will use for the cluster. The disk must be initialized and formatted with an NTFS file format prior to cluster use. When properly configured, both nodes share the same online Basic disk and can access the disk at the same time.

Now that the shared storage witness disk has been configured, we can move on to installing the Windows cluster.

Installing the Failover Clustering Feature

Before a failover clustering can be deployed, the necessary feature must be installed. To install the Failover Clustering feature, perform the following steps:

Running the Validate a Configuration Wizard

Failover Cluster Management is used to administer the Failover Clustering feature. It can be run from Server Manager or as a separate MMC console. After the feature is installed, run the Validate a Configuration Wizard from the tasks pane of the Failover Cluster Management console. All nodes should be up and running when the wizard is run. To run the Validate a Configuration Wizard, perform the following steps:

1.	Log on to one of the Windows Server 2008 R2 cluster nodes with an account with administrator privileges over all nodes in the cluster.
2.	Click Start, click All Programs, click Administrative Tools, and select Failover Cluster Management.
3.	When the Failover Cluster Management console opens, click the Validate a Configuration link in the Actions pane.
4.	When the Validate a Configuration Wizard opens, click Next on the Before You Begin page.
5.	On the Select Servers or a Cluster page, enter the name of a cluster node, and click the Add button. Repeat this process until all nodes are added to the list, as shown in Figure 1, and click Next to continue. Figure 1. Adding the servers to be validated by the Validate a Configuration Wizard.
6.	On the Testing Options page, read the details that explain the requirements for all tests to pass in order to be supported by Microsoft. Select the Run All Tests (Recommended) option button, and click Next to continue.
7.	On the Confirmation page, review the list of servers that will be tested and the list of tests that will be performed, and click Next to begin testing the servers. Note For years, administrators have complained that the Validate a Configuration Wizard window is too small. In Windows Server 2008 R2, administrators can finally resize the window by dragging the lower-right corner. This is not obvious, but try it—it works!
8.	When the tests complete, the Summary page displays the results, and if the tests pass, click Finish to complete the Validate a Configuration Wizard. If the tests failed, click the View Report button to review the details and determine which test failed and why the test failed.

Even if the Validate a Configuration Wizard does not pass every test, depending on the test, creating a cluster might still be possible. After the Validation a Configuration Wizard is completed successfully, the cluster can be created.